1. Field of the Invention
The present invention relates to a rotation angle sensor which is provided with a pedestal for adjustment of a position of a detection element and to a rotary machine
2. Description of the Related Art
Detection of the speed or rotation position or rotation angle of a shaft of a motor or a shaft of a rotary machine which is driven by a motor is important in control of a motor or a rotary machine which is driven by a motor. For this reason, a rotation angle sensor which attaches a rotary body to a shaft of a motor or a shaft of a rotary machine and utilizes magnetism to detect the angle of the rotary body, that is, a “magnetic encoder”, has been known.
Such a rotation angle sensor, for example, as shown in Japanese Patent Publication No. 2006-10436A, is provided with a rotary body of the sensor (detection ring) which is made of a magnetic material which is attached to a shaft for which the rotation angle is desired to be detected and a detection element which is provided with a magnetic detecting part which is arranged around the detection ring. The detection ring is provided with a detected part comprised of relief shapes which are formed at equal intervals on the surface in the peripheral direction (peripheral surface). Further, the detection element is provided with a magnet which is arranged at a position which faces the relief shapes of the detection ring and a magnetic detecting part which is arranged between the magnet and the peripheral surface where the relief shapes are formed. The magnetic detecting part is, for example, formed by applying voltage to a serial circuit of two serially connected magnetoresistance devices which change in resistance in accordance with the magnetic flux density passed. The midpoint voltage of the two magnetoresistance devices changes according to the rotation position of the shaft, whereby the rotation angle of the shaft is obtained.
On the other hand, the position where the rotation angle sensor which detects the rotation angle of the shaft of the motor or the shaft of the rotary machine is set is not always constant. The distance between the detected part of the detection ring and the detection element has to be changed in accordance with the signal strength of the detection signal which is output from the magnetic detecting part. The detection element is used fastened to a pedestal. Therefore, in the past, the distance between the detected part of the detection ring and the detection element has been adjusted by moving the detection element in the radial direction of the detection ring on a radial direction line of the detection ring (line perpendicular to axial line of shaft).
However, the method of adjusting the distance between the detected part of the detection ring and the detection element by moving the detection element in the radial direction of the detection ring is liable to cause the detection element to strike the detection ring and damage the magnetoresistance devices at the inside of the detection element, so there was the problem that the work was difficult.